RESILIENT SEATED BUTTERFLY VALVES

DESIGN FEATURES

1 MOLDED-IN SEAT:

Tightly controlled molding process produces accurate and repeatable dimensions, which leads to consistently lower torques over the valve’s lifetime.

2 PRECISION PROFILED DISC SEALING EDGE:
Extends the valve life by reducing seat wear.

3 ROBUST FLANGE SEALING:
Tear-dropped shaped seat face enables tight sealing with a wide variety of industrial flanges.

4 ISO 5211 TOP FLANGE:
Direct mounting capability between the valve and Bray actuation reduces package height and complexity.

5 UPPER AND LOWER STEM BEARINGS:
Reduce operating torque and increase reliability in high cycle applications.

6 END OF LINE CAPABILITY:
Lug style valve allows for sealing at full rated pressure even when the downstream flange is removed.

LOW PRESSURE DISC

Bray offers a low pressure disc for NPS 2-24 (DN 50-600) Series 3W/3L valves. The purpose of reducing the disc diameter is to decrease the seating/unseating torque and extend the seat life in low pressure applications.

By reducing the disc diameter, the interference between the disc outside diameter and seat inside diameter is decreased and the valve pressure rating, which is a function of this interference, is reduced to 50 psi (3.4 bar). Less interference between the disc and seat results in reduced seating/unseating torque. Lower seating/unseating torque may allow for the use of a smaller actuator on the valve. In other applications where abrasive dry bulk materials such as cement, sugar, plastic, pellets, flour, etc., are generally pneumatically conveyed at 50 psi (3.4 bar) or less, the reduced disc diameter not only reduces the seating / unseating torque but, increases the service life of the seat as well.

Bray does the following to differentiate low pressure discs from full diameter discs:

• Metal discs: An “R” is stamped above the part number to indicate a reduced diameter, low pressure disc.
• Nylon 11 coated discs: Discs are differentiated by the color of the Nylon 11:
  • Gray: Standard pressure
  • White: Low pressure

FLANGE BOLTING TENSIONING

Bray Butterfly Valves with Metal Mating Flanges

A frequently asked question at Bray is “What torque do I apply to the flange bolts to insure the valve is properly installed?”. Initially this seems to be a simple request until all of the factors are analyzed. The installation of a valve requires several components: the valve, mating flanges, nuts, bolts and studs. Each is supplied by different manufacturers and each has different characteristics. The proper torque for one combination may be too much or too little for a second combination. The following is a list of information which needs to be known in order to start calculating the torque requirements.

VALVE

• Type

• Size

• Materials of construction (body)

• Surface finishes / surface conditions

FLANGE

• Type

• Size

• Finish / both sides

• Condition of flange / surface contamination

BOLT (OR STUD)

• Type

• Materials of construction

• Surface conditions

NUT

• Type

• Materials of construction

• Surface conditions

LUBRICATION

• Type

• Coverage

GENERAL FACTORS

• Temperature and relative humidity at the time of

  installation

• Speed at which bolts are turned

Note: The elastomer valve seat manufactured by Bray also acts as the flange gasket. No additional gaskets are required or recommended. Other valve styles which do not have integral gaskets will need to have this component supplied. The characteristics of this component will also need to be
considered.

Complete knowledge of all relevant conditions is almost impossible to obtain. As a result, the computation of the exact torque requirement is not practical. No reputable manufacturer can provide accurate information when so many outside factors are present.

The International Fasteners Institute covers some of the details required to “compute” a torque value. Even with this information the use of a torque wrench is only considered to be 25% accurate. Based on the difficulty and inaccuracy of using this method, Bray recommends the use of the “Turn of the Nut” method.

“Turn of the Nut” Tightening (For Standard Iron and Steel Flanges)

**For Non-Metallic or non-standard flanges, follow the manufacturers installation procedures.

1. The valve and flange faces must be aligned parallel to each other. For rubber seated butterfly valves manufactured by Bray, it is required that the valve be fully opened prior to the tightening of the flange bolts.

2. After aligning the holes in a joint, sufficient bolts shall be placed and brought to a “snug-tight” condition to ensure that the parts of the joint are brought into full contact with each other. “Snug-tight” is the tightness attained by the full effort of a man using a wrench.

3. Following the initial snugging operation, bolts shall be placed in any remaining holes and brought to snug tightness. Re-snugging may be necessary in large joints.

4. Tighten opposite bolts in sequence to insure even pressure around the entire flange.

5. When all bolts are snug-tight, each bolt in the joint then shall be tightened additionally by the applicable amount of nut rotation given in Note 1. During tightening there shall be no rotation of the valve or flange.

NOTE 1
For bolt lengths not exceeding 8 diameters or 8 inches (203.2 mm) = 1/4 turn
For bolt lengths exceeding 8 diameters or 8 inches (203.2 mm) = 1/2 turn

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